When grinding large surfaces, such as the hull of a ship, windmill wings or large tower elements, presently handheld grinding apparatuses are used which are moved back and forth on the surface to be ground.
The person using the grinding apparatus is usually to walk with respiratory protection and safety goggles for protecting himself against the abraded material whirled into the air while using the grinding apparatus.
In the coming years, there will be proposed regulation in Denmark where the use of grinding apparatuses in the outdoors without possibility of collecting the abraded material will either become banned, or very restrictive rules will be set up.
This implies that it will be necessary to grind the items either indoor in a controlled environment, or to provide grinding apparatuses with screening from which the abraded material may be removed.
It will be a great disadvantage if one is obliged to grind everything indoors, since it will imply large costs for establishing workshops that are large enough for e.g. tower elements, ships and the like to be indoor during the grinding process. Furthermore, it may entail large transportation costs in cases where the element to be ground is to be transported to a grinding workshop.
Another problem with grinding large elements or grinding high-level surfaces is that it may be difficult to stand on the ground and guide the grinding apparatus manually. I.e. scaffolding is to be used in order to grind the surface of the elements safely. A solution to this problem is to mount the grinding apparatus on a longitudinally adjustable handle whereby it is possible to reach the top of the element.
The disadvantage of a longitudinally adjustable handle in connection with a commonly known grinding apparatus for grinding approximately vertical surfaces is that it is difficult to apply correct pressure on the grinding disc for ensuring efficient grinding, and that the handle is to have a certain dimension for withstanding the weight of the grinding apparatus. This implies a cumbersome handling of the grinding apparatus and risk of bad surface grinding.
CH-A5-666 648 discloses a handheld grinding apparatus that includes two grinding units, a drive unit and a, screen member, where the two grinding units are enclosed by the screen unit which is arranged with a pipe connection for connecting a suction unit.
The spacer member, which is provided along a lower edge on the screen unit, only has one function, namely to prevent abraded material from being spread to the surroundings, as abraded material spread to the surroundings can be sucked out via the pipe connection.
The disadvantage of this grinding apparatus is that:                the grinding apparatus under use is to be pressed down against a surface, and the applied pressure is to be maintained manually for continuous grinding of the surface. This entails that the operator is to use effort in pressing the grinding apparatus against the surface and to move the grinding apparatus across the surface.        the spacer member, which is adjustable in height and rubber elastic, is deformed by applied pressure and thus only has a sealing function. Applied pressure may, however, also entail that the engagement between the grooves of the spacer member and the lower edge of the screen unit is released, after which the spacer element is pressed upwards onto the lower edge of the screen unit. This results in that the spacer member looses its sealing function, unless the operator is applied further pressure, which may be a drawback as the effect of the grinding is increased thereby.        